1. Field of the Invention
This invention refers to a stacker for the stacking of metallic section bars in alternating straight and reverse layers, in particular of section bars originating from a rolling mill.
2. Discussion of the Background
Those skilled in the art are well familiar with automatic stackers, for example equipped with magnetic heads and auxiliary mechanical devices, capable of stacking metallic section bars originating from a rolling mill or a conveyor, as for example described in the patents EP 0099863, EP 0196685, and EP 0318722.
In these stackers, the rotating heads, generally of a magnetic type, pick up an orderly layer of section bars from a conveying system and position it in a reverse manner on a layer of section bars previously stacked up in an upright manner. This depositing operation occurs on a lowering system arranged in an area reserved for producing the stacks of section bars to be packed.
The rotating heads are generally aided by forward and backward moving trolleys fitted with lances capable, as an alternative to the magnetic heads, of picking up the layers of section bars from the conveying line which must be deposited on the lowering device in an upright position.
In this type of stackers, the rotation of the rotating heads is governed by complex and expensive kinematic devices having, among other things, a rigid geometry.
The mentioned rigidity allows approaching the magnetic heads only up to a certain distance from the last layer of section bars arranged on the lowering device; after this relative approaching motion the stack of section bars is allowed to drop, while demagnetizing the magnetic heads and occasionally employing some expelling devices.
The re-launching and dropping of the section bars from a certain height may lead to a disorderly stacking of the same, and consequently to a poorly assembled package. This is therefore to be avoided for commercial reasons.
Moreover, the potentially improper arrangement of the top layer of section bars may disturb and interfere with the motion of the magnetic heads, with a resulting breakage, jamming problems, and shutdown of the machine. The motion of the magnetic heads is therefore maintained at a certain distance from the top of the layer last deposited on the lowering device, with the result that the deposition of the section bars occurs in an improper manner.
It should also be noted that as the motion of the head carrying a layer of reversed section bars toward a stack of section bars already deposited in an upright manner occurs along an axis not perfectly perpendicular to the plane on which the layer of upright section bars rests, it is not possible to promote the interconnecting of section bars fitted with sections which are difficult to stack.
It should also be highlighted that the known stackers occupy considerable space above the section bars' conveying system. As described in the patent IT 1247451, this encumbrance makes it difficult to access the operating area, both from above or from the sides.
Moreover, the particular complexity of the known kinematic devices used to control the mentioned rotating heads cannot be overlooked. This involves performing numerous operations with a long stacking time, incompatible with the demands on a high productivity of today's and tomorrow's ever more modern rolling mills.
The main object of this invention is to solve the technical problems associated with the known technology, and to produce an automatic stacker capable of depositing, without heavy impacts and in a period of time, a reverse layer of section bars on top of a previously deposited upright layer.
Another object is to avoid a disorderly stacking of the mentioned section bars, resulting in a poor package which may interfere with the motion of the magnetic heads.
Another object of the invention is to produce a stacker equipped with a rotating head maneuvering device of a structurally simple type, capable of not taking up any space above and beside the section bars' conveying line, while at the same time being suitable for an inexpensive production.
These objects are achieved by a stacker provided with the specific characteristics outlined in the attached claims.